SAN FRANCISCO didn't have any reported cases of pediatric AIDS in 1995 or 1996. Pat Christen, Executive Director of the San Francisco AIDS Foundation credits two factors: the city's aggressive drug treatment of pregnant women with HIV and the local needle exchange program.

The one-for-one dirty-for-clean exchange program is subsidized with city dollars, although a violation of state and federal laws. It also may be the reason New York drug injectors have twice the rate of HIV as in San Francisco.

On a recent Thursday, 1,615 needles were turned in at a women's exchange in the Mission District. Women who traded their needles, and those of their lovers and friends, also received food vouchers and a bite to eat. Others saw volunteer medical workers, who drain abscesses, distribute vitamins, give flu shots and pregnancy tests, examine rashes and refer women with hepatitis or pregnancies to full-service clinics.

Volunteer doctor Lisa Packus showed me medical kits they give to heroin addicts who want to kick the habit in a hurry -- which often means by themselves. Workers try to help those who want to get off drugs. There aren't as many takers as you'd like. But recently one woman kicked heroin with the help of such a kit, Packus said.

The dirty clothes, pitted faces and spaced-out look -- HIV Prevention Project head Roslyn Allen said most of the exchangers were under the influence of something "to some extent or another" -- of many exchangers were dead giveaways that they were users. Others didn't look like junkies. Their skin was still clear, their clothes suggested actual employment.

Maria lives in a bus with her boyfriend. Jerry lives on SSI and Social Security. Both said they are not HIV positive. Both believe that without the program, they'd be buying needles on the street. Christen said it is wrong to assume these women don't care about themselves because they're junkies. They do care. They show up Thursdays from 5:30 to 7:30 for clean needles and other treatment.

It's true, when government subsidizes something, it will increase. That principle holds with this program, except that what increases isn't drug use -- federal studies have confirmed -- but needle use. Free clean needles means shooters don't reuse or share needles as often as they used to.

I believe in tough love: no SSI for people because they're substance abusers, arresting those who steal or camp on sidewalks. But while authorities must push the hard tack for the safety of the community, others can offer a hand to these poor souls. Exchange workers reached out to these women and tried to pull them from drug abuse, or failing that, protect them from disease.

Toward the end of the exchange, a mom came with a girl who looked to be 6 or 7. I've seen my share of substance abusing moms and their kids. These two looked about as good as they get. In Reeboks and with her backpack, the mother looked like your everyday working class mom: a little tired. The little girl seemed OK. She didn't have that vacant look you see in neglected kids.

I could never volunteer for this program because I'd call the cops pronto in order to spare that child from likely neglect. Instead, a worker lovingly greeted the little girl and whisked her to a children's area in the back, where she was spared watching her mom stand in an end-of-the-night line of other users, then pull 165 used syringes from her backpack. (No doubt mom was exchanging needles for herself and friends.)

After the mother was given new needles, a worker brought the girl to her mother and they left. I watched them walk down Valencia Street. The little girl was holding her mother's hand and skipping.